Nickel-base and cobalt base alloys and their braze materials are non-magnetic in nature. Gas turbine components are complex in nature and they require joining processes to fabricate the components. Joining processes are also required to repair components after service. Brazing is frequently used to repair components. These repairs from time to time are required to repair defects that have developed in difficult to access locations in some of the components.
Gas turbine hot gas flow path components are often cooled and have complicated internal flow paths. Leaks between inlet and outlet circuits reduce the cooling efficiency leading to oxidation and premature failure of these components. When leaks develop between the circuits, they require correction. These leak paths may be liquid or gas leak paths. The leak paths may have developed as a result of service distress or may simply be the result of fabrication techniques for new parts. For example, casting techniques or welding operations may be the cause of the leak paths, and these techniques and operations may provide such defects in a repetitive manner. Casting techniques are known to produce porosity, and when the porosity is connected, not surprisingly, leak paths may form. Regardless of how the leak paths form, the leak paths must be eliminated or the component may require removal from service.
In many circumstances, repair of defects can be accomplished with standard nickel base or cobalt base brazing material, such as when the defects are readily accessible. However, in many situations, defects may develop in less than desirable locations, making standard repair procedures difficult or impossible. For example, the defect may be in a difficult to reach location, and the available braze alloys that may be used either cannot be properly moved into the location to effect repair or may not have the necessary properties to survive the environmental conditions at the position at which the repair is required.
What is needed is a braze repair material that can withstand harsh environmental conditions that may be experienced in certain components and that readily can be moved to a position to effect repair of the component when standard braze materials cannot be utilized to accomplish the repair.